Audio and Video Technologies for Hardware Developers

  • Article

Microsoft Corporation

Updated October 2003

Summary: This document describes methods by which the Microsoft digital media platform supports the manipulation of data. (4 printed pages)

Introduction

The Microsoft digital media platform includes support for interacting with and manipulating data from a wide variety of hardware devices. Detailed information on the following topics is provided in the Windows Driver Development Kit (DDK) and on Windows Hardware and Driver Central.

  • Acoustic Echo Cancellation
  • Broadcast Driver Architecture
  • 1394 AV/C
  • Global Effects
  • Windows Media Device Manager SDK
  • Windows Media Embedded Product Adaption Kit
  • Kernel Streaming
  • Secure Audio Path: Trusted Audio Drivers
  • DirectX Video Acceleration (VA)

Acoustic Echo Cancellation

In Microsoft® Windows® XP Home Edition and Windows XP Professional, the WDM audio framework supports hardware acceleration of audio-capture effects that are exposed through Microsoft DirectSound®. These effects include acoustic echo cancellation (AEC) and noise suppression. A miniport driver can expose hardware acceleration for any subset of these effects, depending on the capabilities of the underlying device.

For more information on AEC, see DirectSound Capture Effects in the Windows DDK documentation.

Broadcast Driver Architecture

Broadcast Driver Architecture (BDA) minidrivers control digital TV hardware that performs the following operations:

  • Tuning a digital broadcast signal.
  • Demodulating the digital signal.
  • Capturing frames of the digital signal.
  • Demultiplexing the signal into video, audio, and data streams.

For more information on Broadcast Driver Architecture, see BDA Filter Interfaces in the DirectX SDK documentation.

1394 AV/C

Microsoft supports the Audio Video Control (AV/C) protocol, which is built upon the IEC-61883 standard.

The AV/C protocol driver that Microsoft supplies is called avc.sys. It is a functional driver that supports the AV/C subunit protocol. The AV/C subunit protocol is a method for issuing commands and sending responses from subunits on devices such as MiniDV camcorders and digital-VHS tape decks.

For more information, see IEEE 1394 Technology.

Global Effects

Windows XP Home Edition and Windows XP Professional and later provide support for GFX (global effects) filtering of an audio stream. Windows XP supports GFX only for USB devices. A GFX filter can apply an audio-signal transform to the final audio mix that is rendered by an audio device. The effect is global because it affects all of the streams that are combined to form the final mix.

A GFX filter can also process the signal that is captured by an audio device. The GFX filter is inserted into the capture stream before any other processing of the audio signal.

For more information on Global Effects, see GFX Filters in the Windows DDK.

Windows Media Device Manager SDK

The Microsoft Windows Media™ Device Manager SDK helps developers create components that allow applications based on the Windows Media Format SDK to interact with various portable audio players by transferring audio files and manipulating how those files are stored.

The Windows Media Device Manager SDK is intended for use by original equipment manufacturers (OEMs) who produce portable audio players, and independent software vendors (ISVs) who create software that downloads digital media onto those portable audio players. Manufacturers of portable media can also use the Windows Media Device Manager SDK to be sure that their storage devices are recognized properly when working with Windows Media technologies. The Windows Media Device Manager SDK is accessible through C++ applications only.

For more information, see About the Windows Media SDK Components.

Windows Media Embedded Product Adaptation Kit

The Microsoft Windows Media Embedded Product Adaptation Kit (WMEPAK) enables hardware manufacturers to add Windows Media playback to portable digital music players, Internet appliances, and other embedded systems.

For more information, see the Getting Started with the Windows Media Porting Kit.

Kernel Streaming

Audio and video streaming devices are controlled by kernel-mode Windows Driver Model (WDM) minidrivers, which make use of the kernel-streaming layer provided by Microsoft.

Kernel streaming (KS) is a broad term for the services that support kernel-mode processing of streamed data. It enables efficient real-time streaming for multimedia devices such as sound cards and TV tuner cards. Microsoft provides three class drivers, all of which broker interactions between the KS layer and the minidriver:

  • AVStream. Supports both audio and video minidrivers, and should be used for development of new drivers.
  • Port Class.
  • Stream Class.

For more information on kernel streaming, see Windows Kernel Streaming Architecture.

Secure Audio Path: Trusted Audio Drivers

With the release of Secure Audio Path technology in Windows Millennium and Windows XP Home Edition and Windows XP Professional, the data path inside the operating system is protected during transfer from the media player to the sound card. A certified Microsoft component verifies that all downstream components (including the sound card driver) are also certified. It does not decrypt the data stream if it detects unauthorized or compromised components in the execution path.

For more information on Secure Audio Path, see Understanding the Secure Audio Path Model in the Windows Media Rights Manager SDK.

DirectX Video Acceleration (VA)

Microsoft DirectX® Video Acceleration (VA) provides an application programming interface (API) and a corresponding device driver interface (DDI) for acceleration of digital video decoding.

The video acceleration DDI establishes a common interface that provides access to hardware acceleration capabilities. This interface also provides cross-vendor compatibility between user-mode software applications and acceleration capabilities.

For more information, see see DirectX_VA.